<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <div id="app">
      <input type="text" v-model="firstName" />
      <br />
      <input type="text" v-model="lastName" />
      <br />
      <p>{{ fullName }}</p>
    </div>

    <script src="../../Vue.js"></script>
    <script>
      new Vue({
        el: "#app",
        data: {
          firstName: "zhang",
          lastName: "san",
          // fullName: "zhang san",
        },
        // watch: {
        //   firstName(val) {
        //     this.fullName = val + " " + this.lastName;
        //   },
        //   lastName(val) {
        //     this.fullName = this.firstName + " " + val;
        //   },
        // },
        computed: {
          fullName() {
            return this.firstName + " " + this.lastName;
          },
        },
      });
    </script>
  </body>
</html>
